Lined tank and method of constructing and leakage testing the same



P. GRAY April 11, 1944.

LINED TANK AND METHOD OF CONSTRUCTING AND LEAKAGE TESTING THE SAME Filed Dec. 2, 1940 2 Sheets-Sheet l P. GRAY April 11, 1944.

LINED TANK AND METHOD OF GONSTRUCTING AND LEAKAGE TESTING THE SAME Filed Dec. 2, 1940 2 Sheets-Sheet" 2 Patented Apr. 1.1, 1944 UNl'l-E D STATES LINED TANK AND METHOD OF CONSTRUCT- ING AND LEAKAGE TESTING THE SAME Percy Gray, Jefferson, Application December 2, 1940, Serial No. scam In some localities the character of the water is such that ordinary steel tanks used for hot water and the like are subject to corrosion and early failure. At the present time tanks made entirely of-non-corrosive metals such as stainless steel, Monel, etc., are very expensive. Copper, which resists corrosion well, is not so expensive but has relatively low strength, so that it is unsatisfactory for use in the construction of tanks unless reinforced in some way.

It is an object of my invention to provide a construction whereby copper or some similar non-corrosive metal may be used as a lining in steel tanks, the steel furnishing the necessary structural strength.

- It is a further object of my invention to provide a method of making a lined steel tank in which the lining will resist possible distortion in case a vacuum should occur within the tank.

Another object is to provide a method of assembling a lined tank whereby convenient access to theinterior of the tank may be had for performing certain operations in the construction process.

Another object is to provide elements constituting a fitting whereby pipe connections may be made to the finished tank, which elements may be separately attached to the jacket and liner before assembly, and conveniently sealed together after assembly.

Another object is to provide an effective pro-' cedure for testing a lined tank after assembly.

With these and other objects in view my invention consists in the construction, arrangement and combination of the various parts of my device, and in the method of carrying out this construction, whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in my claims and illustrated in the accompanying drawings, in which:

Figure l is a vertical sectional view of an assembled tank embodying the constructional features of -my invention.

Figure 2 is an enlarged fragmentary vertical sectional view of the lower left portion of Figure 1.

Figure 3 is an enlarged fragmentary vertical sectional view of the bushing at the bottom end of the tank in Figure 1.

Figure 4 is an exploded view of the parts entering into the tank assembly.

Figure 5 is a view similar to Figure 3, showing v a modified form of construction of the fittings.

The copper liner is preferably made up in three principal parts, which I have designatedas the 55 together easily.

3 Claims. (01. 'zs-si) top end portion II, the cylindrical intermediate portion l2 and the bottom portion ll. In many cases the top portion II and the bottom portion I can be identical in size and shape. At the s edge of these portions, the material is turned inwardly, as indicated at It. The edges of the cylinder I! are turned outwardly as indicated at It so that a joint may be effected between the parts, as shown between the parts i! Figure 4.

In the center of the end members II and II I I provide a tapered bushing 20 of bronze or other corrosion resisting material. The bushing II is interiorly threaded, as indicated in Figure 3, and is attached to the end memberby brazing or by any other suitable means- The bushing surrounds a hole 22 in the and member to which it is attached.

I provide a steel jacket or shell consisting of end portions 24 and side wall portions 2 and II. Centrally located in the end members 24 are steel sleeves ll which have a tapered bore 32 (Figure '3) with a portion adjacent the inner end of similar taper but smaller'diameter, the latter portion being designated as 34.

Where other openings into the tank are desired I may provide steel sleeves such as it and 88 (Figure 4) which will be subsequently referred to in more detail.

In the assembly of my tank I preferably begin stitute aunitary piece, as illustrated in Figure 4.

The end portion 24 of the steel jacket is joined with the side wall portion II by welding along the line ll. The copper lining assembly, consisting of the cylindrical portion I2 and the end wall 40 portion is, can then be lowered into the jacket assembly consisting of portions 24 and II. When this is done the tapered bushing 2| projecting from the bottom of the copper liner portion will enter the sleeve". The tapered formation of these parts obviously facilitates the assembly,

since the small end of the bushing 22 enters the large end of the sleeve 3|, and is thereby guided into its final position. I

The interior dimensions of the steel jacket are somewhat greater than the exterior dimensions of the copper lining assembly, which makes for ease of assembly, in view of the fact that the parts ordinarily are not perfect in shape, and a little tolerance As an example of the amount and N inis necessary so that they may go of clearance which may be allowed, I have found that approximately one-fourth inch difference in asaasaa means of special tools, the bushing is drawn tightly into the sleeve 3!! and brazed, just as in' the case of the similar fitting at the bottom welded to the steel side portion 26 at the desired points. At corresponding ,points on the copper liner, openings 42 and 44 are made, with diameters somewhat less than the internal diameters copper tube 48 in which an end cap 50 is secured.

by. brazing. A ring or shoulder 52 is attached to the tube 48 by copper welding along the joint indicated at 54. The thermostat pocket assembled as thus described is pushed through the bore of the sleeve 38 from inside the tank. The sleeve 52 serves as a stop, being placed on the tube 48 in such a position that when it bears against the copper lining, the outer end 0! the tube 48 will be just flush with the outer end of the sleeve 38. I then braze the tube 4. to the sleeve II along the Joint 58 as designated in Figure 2, and braze the ring 82 to the lining portion I 2 along the line indicated at It in Figure 2.

The thermostat is inserted into the pocket thus provided, where it can be quickly responsive to the temperature or water within the tank, and

yet can be readily removed without any trouble with packing glands, stuiflng boxes or the like.

The heating element mounting is completed in somewhat the same manner. In this case, however, I provide within the steel sleeve 80 a sleeve 60 of copper, which may be rolled or expanded tightly into the steel sleeve by means'oi a tube roller such as used in attaching tubes to steam boilers. The copper liner portion I2 is flanged into the sleeve 60 in substantially the same way that it was flanged into the enlarged portion 40 of the sleeve 38, The flange" thus formed is brazed to the sleeve iii along the line '4, and the sleeve 60 is brazed to the sleeve 36 all around the joint 8!. a

Flanging the copper liner into the sleeves II and 60, insertion of the thermostat pocket, as

well as the brazing operations in connection therewith, require freedom of access to the interior oi the tank. Aiter these operations have been performed, I complete the copper liner by placing the end portion II on top of the cylindrical portion I2, and braze the joints between the flanges ll and I8.

. The top half of the steel jacket, which may be formed, like the bottom half, of an end portion 24 and a side wall portion 28, is then lowered over the finished copper liner and welded to the lower ting union like that detailed in Figure 3. .By

of the tank. These fittings are for pipe connections to the tank, and while I have shown only two, it will be understood that as many as desired may be provided in the manner described.

The type of end fitting shown in Figure 3 has been referred to in the foregoing description of the assembly operations, but the desired results can be obtained with a modified type oi. fitting such as that illustrated in Figure 5. In the Figure 5Iorm, it will be seen that the oflset in the taper is formed on the inner bushing 20, rather than in the outer sleeve 30, as in the Figure 3 tom. I

in either style, there is a portion 01 relatively short axial length (34 or 34a) at which there will be a tight fit between the bushing 20 and the sleeve 30. Adjacent the outer ends 01' the bushing and sleeve is an annular space I0. As the parts are being assembled, before the bushin is pushed all the way into the sleeve, I insert a ribbon of brazing material, curved in annular shape, into the space l0. Placement 'of the ribbon oi! brazing material in this manner assures good axial alignment of bushing and sleeve when they are subsequently pushed together, and also makes certain that when the brazing material is melted by the application of heat, there is a a complete annular space throughout in which the melted material flows to eflect a perfect seal between bushing and sleeve.

The tight fitting portion 34 or -34a, besides serving as a mechanical support for centering the bushing before the brazing operation, also serves as a stop to prevent the flowoi' brazing material beyond the parts to be Joined and into the space between liner and jacket.

Alter all the joints are sealed as above described, it is obvious that an air space will still be left between the steel jacket and the copper liner as a result of the clearance or tolerance allowed for convenience in assembly. In order that the copper liner shall have the iulladvantage of the structural strength 01 the steel jacket, however, it is desirable that the lining fit tightly against the inside of the Jacket.

To accomplish this result I provide a suitable fitting, such as 14 in Figures 1 and 4, opening into the space between the lining and the jacket. I first fill the tank with water to a test pressure of 300 lbs. to the square inch. Under this pressure the relatively soft and ductile liner is expanded into intimate relation with the jacket. The air in the space between the jacket and liner escapes through the fitting 14.

This first stage of the procedure constitutes'a test of the inner vessel, since it there is any leak in the seams oi the liner, water will escape into the intersp'ace, and will ultimately fiow out through the fitting 14.

I then apply air pressure to the fitting 14 (at vessel, and all the joints at tank openings with a soap solution so that any leaks will be detected. Although I have suggested the use of water and air under pressure for carrying out these tests, it will be apparent that any suitable fluids may be employed for the purpose.

Next a vacuum pump is connected to the fitting 14. After the pressure has been pumped down, I close-o1! thepump connection by a valve and check the permanence of the vacuum by a lents which may be reasonably included within" vacuum gauge in the line between the valve and the fitting 14. If this proves satisfactory, the gauge is removed, the pressure is again pumped down, and the fitting H is sealed on permanently.

Tightness of the joints between jacket and liner at tank openings is important, and is pro- -their scope.

I claim as my invention: 1. In the manufacture of a vessel having an impervious supporting jacket and a relatively thin lining in intimate contact therewith, which lining would readily collapse if it were free to be pulled away from the supporting jacket, as

above, a very small movement of the copper lining away from the steel jacket would immediately increase that volume and establish a partial'v'acuum in the interspace. I provide a high initial vacuum in the interspace, which would ,pre'vent'e'ven slight movement of the cop-,

per lining. As long as the vacuum between lining and jacket were equal to or greater than the vacuum within the tank, there would be no tendency for the lining to. be moved or distorted.

The creation of a vacuum in the interspace takes the place of mechanical bonding between jacket and liner by sweating (soldering) or other means, but can be done much more economically.

Some changes may be made in the details oi forms of structure or use of mechanical equivaby the occurrence of subatmospheric pressure in the vessel, the steps of filling the vessel with fluid under pressure and observing any leakage from the liner to the interspace, introducing between the jacket and the liner gas under a pressure less than that of said fluid and determining any leakage of the jacket, then drawing a vacuum between the jacket and liner and sealing oflthe .space to maintain a subatmospheric pressure therebetween.

2. In the manufacture of a vessel having an impervious supporting jacket and a relatively thin lining in intimate contact therewith, which lining would readily collapse if it were free to be pulled away from the supporting jacket, as by the occurrence of subatmospheric pressurein the vessel, the steps of filling the vessel with fluid under pressure and observing any leakage from. the liner to the interspace, introducing between the jacket and the liner gas under pressure less than that of said fluid, and testing joints in the jacket for leaks. 1

3. A vessel for holding fluid under pressure, having a rigid jacket of relatively hard metal, and a liner of relatively ductile, imperviousmaterial in close contact with the jacket, said lining being sealed to the jacket at all edges, and said vessel having a partial vacuum between the jacket and liner.

l PERCY GRAY. 

